This invention relates to an intake system for an automotive engine and more particularly to an improved high efficiency intake system for such engines.
As is well known, the induction system for an internal combustion engine is very important in determining the performance of the engine. Recently it has been acknowledged that the performance of the engine, at least under some running conditions, can be improved by providing relatively long intake runners that serve the individual ports of the engine. However, in many automotive applications, the use of such long intake runners can give rise to certain problems.
Specifically, a common orientation in modern automotive engine practice is to place the engine transversely in the engine compartment. Such transverse engine placements are employed both in front and rear wheel drive vehicles. However, where the engine is positioned transversely in the engine compartment, it becomes difficult to adequately lengthen the runners of the individual chambers.
One way that the intake runners can be extended is by having them extend from the intake ports and at least in part across the top of the engine toward the opposite side from which the intake ports emanate. Where this is done, however, the intake system tends to lie over a hot portion of the engine such as the cylinder head. As the induction system becomes heated, its efficiency obviously deteriorates as does the performance of the associated engine.
In addition to incorporating long intake runners, it has also been found desirable to position at least one plenum chamber in the induction system. This plenum chamber can most advantageously be positioned at the inlet end to the individual runners. This means that the plenum chamber must either be located over the cylinder head of the engine or, even in extreme cases, over the opposite side of the engine from which the intake ports emanate. When the engine employs a cross flow cylinder head, this means that the plenum chamber will be positioned over the exhaust manifold. Thus the problem of heat transfer to the induction system is even further aggravated.
It may appear that the solution to the aforenoted problem is to increase the distance between the cylinder head and the overlying intake manifold. However, with the emphasis toward lower hood lines to improve aerodynamic efficiency of motor vehicles, it is not possible to raise the intake manifold sufficiently to avoid the aforenoted deleterious effects of heat transfer from the cylinder head and/or exhaust manifold.
It is, therefore, a principal object of this invention to provide an improved induction system for an internal combustion engine.
It is a further object of this invention to provide an improved induction system for an automotive engine wherein long intake runners can be employed but wherein the induction system will not experience undue heating.
It is a further object of this invention to provide an automotive induction system wherein the intake runners may be tuned adequately to improve performance and, at the same time, the runners and their associated plenum chamber will not be disposed close to highly heated portions of the engine.